Not really that important but thought I should mention it.
Just added alt="Pin it" to img on line 416
// FIXED: ADD THE PROTOCOL OR IT WON'T WORK IN SOME SITES
$out .= '<img alt="Pin it" src="https://assets.pinterest.com/images/pidgets/pin_it_button.png" />';
Thanks for fixing the other errors I mentioned, those seem to be validating fine now.